This new conceptual product design resulted from personal experience in the aviation sheet metal industry. Differences in hardness factors between the job tool [rivet gun and detachable snap head] and the material being used [rivets (aluminium) and skins (usually aluminium but often composites)] have always necessitated the continual need to intermittently construct a taped protective surface for the snap portion of the tool. This tool is used for many hours each day. Without protection, the materials utilized in the job often become damaged and must be replaced, thus resulting in significant wastage of both material and work hours. I have clearly observed that this difficulty is experience by virtually all of the individuals who utilize this riveting tool.
Universal (round head) rivets are installed in a variety of methods, but can be divided into two groups, the squeeze type and the impact type methods. The squeeze riveter is either stationary or portable, normally relying on air pressure to compress a rivet. One jaw is stationary and serves as a bucking bar against the manufactured head while the movable jaw upsets the shank and forms the shop head. Compression riveters have their own special rivet sets.
An impact/rivet gun is a piston type tool. Air pressure drives a piston which in turn hammers on a snap or tool head in the rivet gun. In the riveting operation the shop head (or under surface of the rivet) is formed by placing a hardened steel bar against the exposed rivet shank to counter the pressure being applied by the rivet gun. This procedure forms the shop head. The accessibility of the rivets to be installed is not always ideal, thus rivet snaps are available in various sizes, shapes and lengths.
A technician in the field installing rivets is highly skilled, but an ongoing problem occurs. A wide variety of influences, but predominantly the angle of attack (i.e. the snap not being exactly perpendicular to the rivet and skin surface), causes marring, that is, marking or denting (smiles) to occur on either or both the skin and rivet head. This damage also removes the protective coating on the rivet and/or the skin surface thus increasing the chance of early corrosion. In severe cases the fasteners and/or the damaged skin must be repaired or replaced. Of more serious concern is the occurrence of stress risers which may result in cracks potentially leading to a compromise of structural integrity.
For years, in an attempt to reduce or avoid this problem technicians in the field have been applying tape (masking, electrical etc.) to the end of the rivet snap to provide a buffer zone. Taping is limited in that only a small number of fasteners can be installed before the snap requires re-taping. This procedure is quite time consuming and messy due to the adhesive.
It is known in regard to tools for impacting flush type rivets, that is rivets which provide a flat face coplanar with the finished material, that the tool face include a recessed rubber ring around the edge of the flat tools face. The majority of the rivet is therefore impacted by the metal inner portion of the tool head while the surrounding rubber ring which is flush with or slightly proud of the metal surface inhibits marring of the material surrounding the rivet.
A similar arrangement, in which the angle of attack can be varied, includes a tool head which is mounted on a support ball so that it can be swivelled to the required angle on the ball. The tool head is surrounded by a rubber sleeve which again is flush with the end face or slightly proud of the end face so as to provide a ring surrounding the end face.
In both of these arrangements, the rivet is impacted by the metal tool and the rubber ring surrounds the tool to reduce the possibility of marring.
However the solution is unsuitable for recessed head of a tool used for domed rivets or universal rivets and no solution for the marring effect of the tool for such rivets has been provided.